pH-Responsive Biomaterials for the Treatment of Dental Caries-A Focussed and Critical Review

Two-stepped pH-responsive peptide microsphere/carboxymethyl chitosan complex: enhanced protection of an inflamed dentin-pulp complex

Dental caries is the most prevalent infectious disease affecting oral health, leading to the destruction of tooth hard tissues and dental pulp inflammation. The dentin-pulp complex, as the biological core of the tooth, can generate reparative dentin to protect the dental pulp from infection progression. However, untreated carious lesions chronically disrupt the structural integrity and reparative capacity of the dentin-pulp complex, thereby significantly compromising pulp vitality as deep caries progresses. In this study, a two-stepped pH-responsive peptide microsphere/carboxymethyl chitosan complex (PM/CS) was designed to offer comprehensive protection for the inflamed dentin-pulp complex. PM/CS has a three-dimensional network structure, and it constructs an intelligent drug delivery system by integrating TVH-19 self-assembled peptide microspheres that we developed earlier into carboxymethyl chitosan. This complex not only exhibited pH-controlled release characteristics, but also showed antibacterial properties against Streptococcus mutans and a mineralization-promoting effect on human dental pulp cells (hDPCs). PM/CS exerted acute anti-inflammatory effects on early pulpal lesions in rats, while longitudinal studies revealed its remarkable capacity to induce tertiary dentinogenesis, indicating therapeutic efficacy through biological modulation. This study provides a potential pulp capping complex material for the restoration treatment of the dentin-pulp complex under the influence of deep caries.

Dendritic polyglutamic acid-chelerythrine nanocomplex for the reversal of bacterial tooth decay

Caries begin with an imbalance between demineralization and remineralization due to the continuous acid production by cariogenic bacteria. However, the development of dental materials that could prevent and treat caries via a simple and efficient mechanism has always been a challenge. To address this issue, therapeutic nanoparticles composed of a dendritic polyglutamic acid (DPGlu) and chelerythrine (CHE) complex (DPGlu@CHE) were developed via hydrophobic interactions and hydrogen bonds. DPGlu@CHE could be adsorbed onto the tooth surface, releasing CHE rapidly under acidic conditions to remove cariogenic bacteria, subsequently inducing tooth surface remineralization in situ. Our results demonstrated that more than 99% of Streptococcus mutans on the tooth surface were killed, and 84% of the mechanical properties of tooth were restored within 2 weeks. Thus, DPGlu@CHE was proven to be a safe and effective enamel restoration material in vitro, and its safety was verified in vivo, making it a promising mouthwash ingredient to maintain dental health.

Development and Evaluation of Gelatin-Based Gummy Jellies Enriched with Oregano Oil: Impact on Functional Properties and Controlled Release

Functional foods play a crucial role in contemporary dietary strategies. This study investigates the incorporation of oregano oil, a bioactive extract that is known for its antimicrobial and antioxidant properties, into gelatin-based gummy jellies to develop functional food products with controlled release properties. The jellies were evaluated for mass uniformity, swelling index, disintegration time, and tensile strength under simulated oral and gastric conditions. The results showed that oregano oil significantly reduced the swelling index (e.g., 128.76 ± 0.67% at pH 5) and prolonged the disintegration time (e.g., 6-18 min across pH environments), highlighting its potential for controlled release. The mechanical strength remained stable (5.2 ± 0.3 N), ensuring structural integrity. These findings suggest that oregano-oil-enriched gummy jellies offer health benefits, although further studies are needed to explore their long-term stability and bioavailability.

Trends in pH-triggered strategies for dental resins aiming to assist in preventing demineralization: A scoping review

OBJECTIVES

To identify and map the literature on the current state of pH-triggered strategies for resin-based materials used in direct restorative dentistry, focusing on innovative compounds, their incorporation and evaluation methods, and the main outcomes.

DATA AND SOURCES

Through a search across PubMed, Scopus, Embase, Web of Science, LILACS, Cochrane Library databases, and Google Scholar, this review identified studies pertinent to pH-responsive dental materials, excluding resin-modified glass ionomer cements.

STUDY SELECTION

From the 981 records identified, 19 in vitro studies were included, concentrating on resin-based composite resins (50 %), dentin adhesives (25 %), and sealants (25 %). The review identified diverse pH-triggered strategies based on ion release, antibacterial release, antibacterial no release, association of contact-antibacterial compounds with acid neutralizer, and combined ion and antibacterial releasing systems for the development of pH-responsive dental materials. Despite the incorporation of innovative compounds such as nanoparticulated amorphous calcium phosphate (20 %), tetracalcium phosphate (40 %), chlorhexidine-loaded mesoporous silica nanoparticles (10 %), tertiary amine dodecylmethylaminoethyl methacrylate (5 %), and bioactive glass with 4 % nano-POSS (20 %), the mechanical integrity of the materials remained satisfactory, displaying flexural strength and elastic modulus that were similar to or better than control. Materials showcased pH-dependent release of calcium and phosphate ions, especially in acidic conditions, and potential for prevention of tooth demineralization, indicating decreased mineral loss and lesion depth.

CONCLUSIONS

In general, ion releasing and antibacterial-based strategies alone or associated, comprising the incorporation of amorphous calcium phosphate, tetracalcium phosphate, chlorhexidine-loaded mesoporous silica nanoparticles, tertiary amine dodecylmethylaminoethyl methacrylate, and bioactive glass with 4 % nano-POSS were used to provide pH-responsiveness for composite resins, adhesive systems, or sealants, without compromise of the mechanical properties, and with promising potential for enhancing caries prevention.

CLINICAL RELEVANCE

Advancements on smart pH-responsive dental resins based on ion-releasing and antibacterial associated strategies may contribute to prevent or reduce bacterial acid formation and demineralization of tooth structure at the interface between tooth tissues and restoration, possibly favoring the success of restorative treatment in the future.

Cariogenic Microbiota and Emerging Antibacterial Materials to Combat Dental Caries: A Literature Review

Dental caries is the most common oral disease in the world and a chronic infectious disease. The cariogenic microbiome plays an important role in the process of caries. The ecological imbalance of microbiota leads to low pH, which causes caries. Therefore, antibacterial materials have always been a hot topic. Traditional antibacterial materials such as cationic antibacterial agents, metal ion antibacterial agents, and some natural extract antibacterial agents have good antibacterial effects. However, they can cause bacterial resistance and have poor biological safety when used for long-term purposes. Intelligent antibacterial materials, such as pH-responsive materials, nanozymes, photoresponsive materials, piezoelectric materials, and living materials are emerging antibacterial nano-strategies that can respond to the caries microenvironment or other specific stimuli to exert antibacterial effects. Compared with traditional antibacterial materials, these materials are less prone to bacterial resistanceand have good biological safety. This review summarizes the characteristics of cariogenic microbiota and some traditional or emerging antibacterial materials. These emerging antibacterial materials can accurately act on the caries microenvironment, showing intelligent antibacterial effects and providing new ideas for caries management.

Stimulus-responsive smart bioactive glass composites for repair of complex tissue defects

Smart biomaterials with active environmental responsiveness have attracted widespread attention in recent years. Previous studies on bioactive glass (BG) have mainly focused on the property of bioactivity, while little attention has been paid to the property of smart response of BG. Herein, we propose the concept of Smart Bioactive Glass Composites (SBGC) which are capable of actively responding to the endogenous disease microenvironment or exogenous physical stimuli, thereby enabling active treatment of tissue defect sites and ultimately promoting tissue regeneration. In this review, the response characteristics of SBGC to different internal and external environments are described. Subsequently, the applications of SBGC in complex tissue defect repair of tumors, infections, and diabetes are reviewed. By deeply analyzing the recent progress of SBGC in different fields, this review will point out the direction for the research of next-generation BG.

Review and Future Perspectives of Stimuli-Responsive Bridged Polysilsesquioxanes in Controlled Release Applications

Bridged polysilsesquioxanes (BPSs) are emerging biomaterials composed of synergistic inorganic and organic components. These materials have been investigated as ideal carriers for therapeutic and diagnostic systems for their favorable properties, including excellent biocompatibility, physiological inertia, tunable size and morphology, and their extensive design flexibility of functional organic groups to satisfy diverse application requirements. Stimuli-responsive BPSs can be activated by both endogenous and exogenous stimuli, offering a precise, safe, and effective platform for the controlled release of various targeted therapeutics. This review aims to provide a comprehensive overview of stimuli-responsive BPSs, focusing on their synthetic strategies, biocompatibility, and biodegradability, while critically assessing their capabilities for controlled release in response to specific stimuli. Furthermore, practical suggestions and future perspectives for the design and development of BPSs are presented. This review highlights the significant role of stimuli-responsive BPSs in advancing biomedical research.

Nanoparticles and bone microenvironment: a comprehensive review for malignant bone tumor diagnosis and treatment

Malignant bone tumors, which are difficult to treat with current clinical strategies, originate from bone tissues and can be classified into primary and secondary types. Due to the specificity of the bone microenvironment, the results of traditional means of treating bone tumors are often unsatisfactory, so there is an urgent need to develop new treatments for malignant bone tumors. Recently, nanoparticle-based approaches have shown great potential in diagnosis and treatment. Nanoparticles (NPs) have gained significant attention due to their versatility, making them highly suitable for applications in bone tissue engineering, advanced imaging techniques, and targeted drug delivery. For diagnosis, NPs enhance imaging contrast and sensitivity by integrating targeting ligands, which significantly improve the specific recognition and localization of tumor cells for early detection. For treatment, NPs enable targeted drug delivery, increasing drug accumulation at tumor sites while reducing systemic toxicity. In conclusion, understanding bone microenvironment and using the unique properties of NPs holds great promise in improving disease management, enhancing treatment outcomes, and ultimately improving the quality of life for patients with malignant bone tumors. Further research and development will undoubtedly contribute to the advancement of personalized medicine in the field of bone oncology.

pH-responsive membranes: Mechanisms, fabrications, and applications

Understanding the mechanisms of pH-responsiveness allows researchers to design and fabricate membranes with specific functionalities for various applications. The pH-responsive membranes (PRMs) are particular categories of membranes that have an amazing aptitude to change their properties such as permeability, selectivity and surface charge in response to changes in pH levels. This review provides a brief introduction to mechanisms of pH-responsiveness in polymers and categorizes the applied polymers and functional groups. After that, different techniques for fabricating pH-responsive membranes such as grafting, the blending of pH-responsive polymers/microgels/nanomaterials, novel polymers and graphene-layered PRMs are discussed. The application of PRMs in different processes such as filtration membranes, reverse osmosis, drug delivery, gas separation, pervaporation and self-cleaning/antifouling properties with perspective to the challenges and future progress are reviewed. Lastly, the development and limitations of PRM fabrications and applications are compared to provide inclusive information for the advancement of next-generation PRMs with improved separation and filtration performance.

Development of "Intelligent particles" for the treatment of dental caries

Dental caries is one of the most prevalent non-communicable diseases worldwide, mediated by a multispecies biofilm that consists of high levels of acidogenic bacteria which ferment sugar to acid and cause teeth demineralization. Current treatment practice remains insufficient in addressing 1) rapid clearance of therapeutic agents from the oral environment 2) destroying bacteria that contribute to the healthy oral microbiome. In addition, increasing concerns over antibiotic resistance calls for innovative alternatives. In this study, we developed a pH responsive nano-carrier for delivery of polycationic silver nanoparticles. Branched-PEI capped silver nanoparticles (BPEI-AgNPs) were encapsulated in a tannic acid - Fe (III) complex-modified poly(D,L-lactic-co-glycolic acid) (PLGA) particle (Fe(III)-TA/PLGA@BPEI-AgNPs) to enhance binding to the plaque biofilm and demonstrate "intelligence" by releasing BPEI-AgNPs under acidic conditions that promote dental caries The constructed Fe(III)-TA/PLGA@BPEI-AgNPs (intelligent particles - IPs) exhibited significant binding to an axenic S. mutans biofilm grown on hydroxyapatite. Ag+ ions were released faster from the IPs at pH 4.0 (cariogenic pH) compared to pH 7.4. The antibiofilm results indicated that IPs can significantly reduce S. mutans biofilm volume and viability under acidic conditions. Cytotoxicity on differentiated Caco-2 cells and human gingival fibroblasts indicated that IPs were not cytotoxic. These findings demonstrate great potential of IPs in the treatment of dental caries.

Harnessing the Power of Stimuli-Responsive Nanoparticles as an Effective Therapeutic Drug Delivery System

The quest for effective and reliable methods of delivering medications, with the aim of improving delivery of therapeutic agent to the intended location, has presented a demanding yet captivating field in biomedical research. The concept of smart drug delivery systems is an evolving therapeutic approach, serving as a model for directing drugs to specific targets or sites. These systems have been developed to specifically target and regulate the administration of therapeutic substances in a diverse array of chronic conditions, including periodontitis, diabetes, cardiac diseases, inflammatory bowel diseases, rheumatoid arthritis, and different cancers. Nevertheless, numerous comprehensive clinical trials are still required to ascertain both the immediate and enduring impacts of such nanosystems on human subjects. This review delves into the benefits of different drug delivery vehicles, aiming to enhance comprehension of their applicability in addressing present medical requirements. Additionally, it touches upon the current applications of these stimuli-reactive nanosystems in biomedicine and outlines future development prospects.

Exploring the Horizons of Four-Dimensional Printing Technology in Dentistry

In dentistry, the integration of additive manufacturing, particularly 3D printing, has marked significant progress. However, the emergence of 4D printing, which allows materials to change shape dynamically in response to stimuli, opens up new avenues for innovation. This review sheds light on recent advancements and potential applications of 4D printing in dentistry, delving into the fundamental principles and materials involved. It emphasizes the versatility of shape-changing polymers and composites, highlighting their ability to adapt dynamically. Furthermore, the review explores the challenges and opportunities in integrating 4D printing into dental practice, including the customization of dental prosthetics, orthodontic devices, and drug delivery systems and also probing into the potential benefits of utilizing stimuli-responsive materials to improve patient comfort, treatment outcomes, and overall efficiency and the review discusses current limitations and future directions, emphasizing the importance of standardized fabrication techniques, biocompatible materials, and regulatory considerations. Owing to its diverse applications and advantages, 4D printing technology is poised to transform multiple facets of dental practice, thereby fostering the development of healthcare solutions that are more tailored, effective, and centered around patient needs.

New Nano-Crystalline Hydroxyapatite-Polycarboxy/Sulfo Betaine Hybrid Materials: Synthesis and Characterization

Hybrid materials based on calcium phosphates and synthetic polymers can potentially be used for caries protection due to their similarity to hard tissues in terms of composition, structure and a number of properties. This study is focused on the biomimetic synthesis of hybrid materials consisting of hydroxiapatite and the zwitterionic polymers polysulfobetaine (PSB) and polycarboxybetaine (PCB) using controlled media conditions with a constant pH of 8.0-8.2 and Ca/P = 1.67. The results show that pH control is a dominant factor in the crystal phase formation, so nano-crystalline hydroxyapatite with a Ca/P ratio of 1.63-1.71 was observed as the mineral phase in all the materials prepared. The final polymer content measured for the synthesized hybrid materials was 48-52%. The polymer type affects the final microstructure, and the mineral particle size is thinner and smaller in the synthesis performed using PCB than using PSB. The final intermolecular interaction of the nano-crystallized hydroxyapatite was demonstrated to be stronger with PCB than with PSB as shown by our IR and Raman spectroscopy analyses. The higher remineralization potential of the PCB-containing synthesized material was demonstrated by in vitro testing using artificial saliva.

pH-responsive polymeric nanomaterials for the treatment of oral biofilm infections

Bacterial and fungal pathogens forming oral biofilms present significant public health challenges due to the failure of antimicrobial drugs. The ability of biofilms to lower pH levels results in dental plaque, leading to gingivitis and cavities. Nanoparticles (NPs) have attracted considerable interest for drug delivery and, thus, as a solution to biofilm-related microbial infections. A novel strategy in this regard involves using pH-responsive polymeric NPs within the acidic microenvironment of oral biofilms. The acidity of the oral biofilm microenvironment is governed by carbohydrate metabolism, accumulation of lactic acid, and extracellular DNA of extracellular polymeric substances by oral biofilm-forming microbial pathogens. This acidity also provides an opportunity to enhance antibacterial activity against biofilm cells using pH-responsive drug delivery approaches. Thus, various polymeric NPs loaded with poorly soluble drugs and responsive to the acidic pH of oral biofilms have been developed. This review focuses on various forms of such polymeric NPs loaded with drugs. The fundamental mechanisms of action of pH-responsive polymeric NPs, their cytological toxicity, and in vivo efficacy testing are thoroughly discussed.